The present invention relates to a hybrid digital-optical radar signal processor which is designed for use with a radar having multiple transmit frequencies and an associated multi-channel search receiver.
Because of the Fourier Transform properties of a lens, signal processors using coherent optical correlators possess a potentially significant advantage in size and cost as compared to their electronic counterparts. This is particularly true for coherent signal processing whenever multi-channel or two dimensional correlations are involved. Recent emphasis in optical computing has been placed upon either film processors or ultrasonic modulators. Both of these approaches have deficiences when considered for a real time radar environment. The film type processors are too slow. The Ultrasonic modulators do possess adequate speed but have other limitations which adversely affect overall system flexibility. Specifically, signal delay accomplished by propagation in the ultrasonic medium is limited to about 100 microseconds. This limits the integration time accordingly. In addition, changes in pulse width and pulse separation cannot be effected over a substantial range, which limits the choice of possible transmit waveforms. Finally, unless auxiliary means are used, signals transduced into the ultrasonic medium are lost.
The principal object of the present invention, therefore, is to provide a hybrid digital-optical radar signal processor which will take advantage of the benefits of an optical processor while retaining the flexibility of a digital system.
Another important object is to provide a signal processor which uses no moving parts and which, therefore, has high mechanical stability and no substantial registration problems.
A further object of the invention resides in the provision of a signal processor which does not involve difficult control techniques or the use of dangerous materials.
As still another object the invention provides a hybrid digital-optical radar signal processor which may be packaged into a compact, rugged assembly and which will therefore be reliable in operation.
Other objects and advantages of the invention will be readily appreciated as the description thereof proceeds.